How to track state of a button

I have a button on page and want to show a error popup while user clicks it more than once. What would be the best approach for the same.

You should store this information in the template of your button.

For example :

<template name="MyTemplate">
  <button>Click me</button>
Template.MyTemplate.onCreated(function () {
  this.buttonAlreadyClicked = false;
  'click button': function (event, template) {
    if ( template.buttonAlreadyClicked ) {
      // show popup
    } else {
      template.buttonAlreadyClicked = true;
      // do something else